Table 2.

Qualities of included studies based on modified Newcastle‐Ottawa Scale

Study	Case definition	Representativeness	Selection of controls	Definition of controls	Comparable for therapy	Comparable for etiology	Assessment of outcomes	Integrity of follow‐up	Quality score
Auezova et al.11, Lebanon	1	1	0	1	1	1	1	1	7
Bambury et al.18, Ireland	1	1	0	1	1	0	1	1	6
Bao et al.19, China	1	1	0	1	0	1	1	1	6
Gandhi et al.20, India	1	1	1	1	0	1	1	0	6
Han et al.21, China	1	1	0	1	1	0	1	1	6
He et al.22, China	1	1	0	1	1	1	1	1	7
Kaya et al.23, Turkey	1	1	0	1	1	0	1	1	6
Liang et al.24, China	1	1	0	1	1	0	1	1	6
Lopes et al.25, Portugal	1	1	0	1	1	0	1	1	6
Mason et al.26, Canada	1	1	0	1	1	0	1	1	6
McNamara et al.27, Canada	1	1	0	1	1	0	1	1	6
Wang et al.28, China	1	1	0	1	1	1	1	1	7
Wang et al.9, China	1	1	0	1	0	1	1	1	6
Wang et al.29, China	1	1	0	1	0	1	1	0	5
Weng et al.30, China	1	1	0	1	1	1	1	1	7
Xu et al.31, China	1	1	0	1	1	0	1	1	6
Yersal et al.32, Turkey	1	1	0	1	1	0	1	1	6
Zhou et al.33, China	1	1	0	1	1	1	1	1	7